2. Prenatal Diagnosis
• Over the last 4 decades, the genetic basis of
an increasing number of diseases is becoming
understood. At the same time, safe and
effective fetal diagnostic techniques are being
developed.
3. Prenatal Diagnosis of fetal
Abnormalities
• Benefits:
1.Malformation incompatible with life may be
terminated.
2.Certain abnormalities may be correctible in-utero.
3.-Provides opportunity to arrange corrective
measures before hand.
- offer a chance to be delivered at a place where
the required facilities are available.
4. Parents decision to continue pregnancy/ mentally
prepare to have a handicapped child.
5. What Should We Do?
• Every pregnancy should be evaluated with the
most definite test.
• Practically & economically not feasible because
expensive
Invasive
Worldwide practice is to carry out
-Screening procedures
-Definite (diagnostic)tests for screening
positive cases
7. Screening Procedures --- Cont.
1. History:
- Increasing maternal age
- Congenital anomalies in previous children
- F/Hx.
. Still birth
. Recurrent 1st
trimester abortion
. Cousin marriage
8. Screening Procedures ---Cont.
2. Features of current pregnancy:
- Drug intake(antiepileptics e.g. warfarin,
alcohol, smoking)
- Radiation exposure
- Maternal ch. diseases e.g.DM, cardiac, renal
- Uterine fundas large/ small for date
- Decrease fetal movements
- Fetal malpresentation
- Viral infection in early pregnancy
9. Screening Procedures --- Cont.
3. Ultrasonography:
- Screening tool in all trimesters
- At 10-14 weeks if fetal nuchal translucency
- > 2.5 mm- chromosomal anomalies
association
- At 18-20 weeks 75% fetal abnormalities
can
be diagnose
16. Screening Procedures ---Cont.
4. Maternal blood tests:
- Maternal Serum alpha fetoproteins:
. Produced by
. Fetus &enter in maternal circulation.
. Yolk sac in first trimester
. Liver in second and third trimester
. Normally increase from 12-32 weeks
. Abnormally raise on fetal capillaries
exposure to amniotic fluid e.g. in NTD.
17. Maternal S. alpha fetoproteins --cont.
- Raised level in neural tube defect(NTD).
- Screen for NTD at 15-20 weeks if +ve confirm
with detailed USG.
- Also raised in following conditions:
. Miscalculated dates . Multiple pregnancies
. Threatened abortion . IUD
. Teratoma . Congenital nephrosis
. Ant. Abdominal wall defects
20. Triple Test
• - Used for Down Synd. Screening. It comprises
. AFP
. hCG
. uE3 (unconjugated oestriol )
- Best carried at 15-18 weeks. In DS AFP & uE3
are low while hCG is raised
- Triple test+ maternal age diagnose 60% DS
- In trisomy 18 all above components are low
21. Quadruple test
• Triple test+ Inhibin A estimation
• This test + maternal age detects 76% DS
22. Double Test
• Low pregnancy associated plasma proteins-A
(PAPP-A) level and raised serum Beta-hCG
during 1st
trimester
• Double test+ maternal age diagnose 60% DS.
26. DIAGNOSTIC TESTS
• For high risk women on basis of screening tests
• An ideal test should be :
- Least invasive
- diagnose c. abnormality in early pregnancy.
- Minimally interfering developing pregnancy
• Diagnostic tests are also not risk free.
27. Counselling
• Organize an appointment
• Couple should be present
• Explain:
- Risk of occurance of c. abnormality
- All tests available, their procedure, cost,
diagnostic ability and benefits, possible risks
- Possible management plain
• If termination of pregnancy is unacceptable
diagnostic tests would be fruitless.
28. NON INVASIVE TESTS
• Ultrasonography:
• Diagnostic USG is different from screening USG,
- It takes longer time
- Dx. Wide range of c. anomalies
- Non invasive and diagnosis at spot possible
- But possible only at large gestational age
• Colour doppler further enhance the capability
especially for cardiac malformations and renal
agenesis.
29. Other Soft Signs
• short ears
• cerebellar hypoplasia
• cholecystomegaly
• Mild cerebral ventriculomegaly
• Hypoplasia of middle phalanx of 5th digit
• Increased Iliac angle
• Short frontal lobe
30. What are the 2T soft signs?
• Increased nuchal thickness
• short femur or humerus
• Pylectasis
• echogenic foci in heart
• Echogenic Bowel
• choroid plexus cysts
31. INVASIVE TESTS
AMNIOCENTESIS:
• Aspiration of amniotic fluid which contain fetal
cells
• Fluid can be used for estimation of
- bilirubin level (for fetal haemolytic disease).
- AFP
-Acetyl cholinesterase
• Cells used for karyotyping (Chromosomal dis.)
• Fetal cells-cultured for 3 weeks- karyotyping.
• New technique-PCR, FISH-give result in 48 h.
32. AMNIOCENTESIS---Cont.
• Procedure:
• Preliminary USG to confirm-duration of gestation,
-placental site,- adequacy of liqour (150-200 ml)
• Sterilize the abdomen
• 22 G spinal needle is used.
• About 20 cc amniotic fluid is withdrawn.
• Give Anti- D to all Rh-ve mothers.
• Ask rest for 30 min.& restrict movements for 48h
34. AMNIOCENTESIS---Cont.
• Limitations (difficulties)of procedure: if
- Anteriorly placed placenta
- Multiple pregnancy.
- Maternal obesity
- Oligohydramnios
• Risks:
- Pregnancy loss 1 % - Bleeding , Infection,
- Rupture of membrane - Preterm labour&IUD
- Leaking of Amniotic fluid
- Increase risk of RDS in newborn
35. CHORIONIC VILLUS SAMPLING
• Collection of fragments of placental tissue (chorionic
villi)- cells are examined for Dx. of C.Anomalies.
• Cytotrophoblastic (rapidly dividing) cells are used for
direct karyotyping- result available within 24-48 h.
• Chorionic villi are best source of DNA
• CVS can be performed at 10 weeks gestation.
• Indications:
1-DNA analysis for SCD,thallasemias, CF. hemophillias
2-Chromosomal abnormalities
3-Inborn error of metabolism
36. CHORIONIC VILLUS SAMPLING
• Procedure:
• Trans-abdominal approach preferred –under USG
guidance in supine position
• Trans-cervical approach is easy.
• In lithotomy position, sterilize area & Aspiration
catheter and biopsy forceps.
• Introduce through Cx. under USG into placental
tissue avoiding membrane rupture
• Risks: Pregnancy loss 2-6%
• Before 10 weeks- associated with limb deformities,
micrognathia, microglassia
37.
38.
39. FETAL BLOOD SAMPLING (FBS)
• Fetal blood- lymphocyte are rapidly cultured, results
within 48-72 hours.
• Indications: 1- Prenatal Dx. DNA available for
Cytogenetic studies In failed amniocentesis, and
mosaicism in chorion or amniotic fluid.
2-Fetal assessment: for red cell alloimmunization,
(Hb;Hc,TrF) Hydrops fetalis, viral infection, platelets
alloimmunization
• Unfortunately Associated with highest rate of fetal loss.
• Currently used for blood transfusion in-utero in fetal A.
40. FETAL BLOOD SAMPLING (FBS)
• Procedure : (cordocentesis):
• The sites for FBS are placental insertion of
umbilical cord, abdominal insertion of cord,
intrahepatic fetal vein and fetal heart.
• Suitable time is 20-28 weeks
• Risks:
- Bleeding from site of puncture
- Cord haematoma
- Fetal bradycardia
- Fetal death
41. EMBRYOSCOPY & FETOSCOPY
• Direct visualization of embryo and fetus.
• Limited field of vision.
• Provide information only about external fetal
structures .
42. NEW MOLECULAR ANALYTIC
TECHNIQUES
• Fetal cell obtained by CVS and Amniocentesis
can be used for prenatal Dx. For congenital
anomalies by following new techniques
1- Southern blotting:
Cleavage of chromosomal DNA at specific
sites and used for tests
2- PCR
3- FISH
43. Polymerase chain reaction (PCR)
• Amplify specific DNA and RNA fragments
• Once nucleotide sequence of a region of DNA
strand is known, complimentary
oligonucleotides & polymerase are added to
single strand DNA
• Repeat process 30 times to get adequate DNA
• PCR identify specific DNA sequence for gene
mutation & prenatal Dx. at an earlier stage
before an embryo transfer in IVF cycle.
44. FLOURESCENT IN SITU HYBRIDIZATION
• FISH allows detection & localization of specific
DNA sequence in interphase or metaphase.
• Advantage – results available in 24-48 h.
• Disadvantage – fail to detect big structural
rearrangements
• Identify 80% clinically relevant abnormalities,
helpful for early decision about further
management of affected pregnancies.
45. MANAGEMENT OF FETAL C. ANOMALIES
• It is a tedious task, requires skillful,
sympathetic & professional approach.
• Management options
- Termination of pregnancy
- In- utero management if possible
- Conservative management
46. POSTPARTUM MANAGEMENT OF C.A.
For better understanding of congenital anomalies
and its impact on future reproductive performance of
couple, following procedures are carried out on
affected babies/ abortusses:
1.Physical examination /postmortem
2.Fetal tissue(blood, skin, placenta) for karyotyping
3.Placenta and membrane for histopathology
4.Placental & baby swab for microbiology & virology.
5.Baby gram (x-rays of whole baby)
6.Baby photograph
